Three-dimensional display device and three-dimensional display method

1. A three-dimensional display device configured to display a main image and an additional image on a screen, the three-dimensional display device comprising: a possibly-unsuitable region decider that decides, based on a predetermined depth range within the main image, a first region and a second region that are possibly unsuitable for the additional image to be superimposed on the main image, the first region having a depth that protrudes beyond the predetermined depth range toward a near side of the screen, and the second region having a depth that protrudes beyond the predetermined depth range toward a far side of the screen that is recessed relative to the first region; a display region candidate decider that decides one candidate region from a plurality of region candidates for the additional image to be superimposed on the main image on the screen, wherein the plurality of region candidates includes the first region and the second region decided by the possibly-unsuitable region decider; a depth suitability determiner that determines, based on a boundary region that is within a predetermined distance from a boundary line between the candidate region and outside of the candidate region in the main image, whether a difference between a depth of the main image displayed at the boundary region and a depth of the additional image is within a predetermined tolerance range; and an image composer that, when it is determined that the difference in depth between the depth of the main image displayed at the boundary region and the depth of the additional image is within the tolerance range, superimposes the additional image upon the main image at the candidate region, thereby composing a composite image of the main image and the additional image, and displays the composite image on the screen.

2. The three-dimensional display device according to claim 1 , wherein, when it is determined that the difference in depth is not within the tolerance range, the display region candidate decider re-decides the candidate region.

3. The three-dimensional display device according to claim 1 , wherein the depth suitability determiner divides the boundary region into a predetermined number of partial regions, calculates a difference in depth between the depth of the main image displayed at the partial region and the depth of the additional image for each partial region, and determines whether or not a maximum value of the calculated difference in depth is within the tolerance range, thereby determining whether or not the difference in depth between the depth of the main image displayed in the boundary region and the depth of the additional image is within the predetermined tolerance range.

4. The three-dimensional display device according to claim 1 , wherein the image composer, when it is determined that the difference in depth is within the tolerance range, composes, as the composite image, an image where the additional image having a first frame is superimposed on the candidate region on the main image, and displays the composite image on the screen, and when it is determined that the difference in depth is not within the tolerance range, composes, as the composite image, an image where the additional image having a second frame, which is broader than the first frame, is superimposed on the candidate region on the main image, and displays the composite image on the screen.

5. The three-dimensional display device according to claim 1 , further comprising: a display-forbidden region storage that stores a display-forbidden region, which is a region on the screen where display of the additional image is forbidden, wherein the display region candidate decider decides one candidate region from the plurality of region candidates of the additional image, which does not overlap the display-forbidden region.

6. The three-dimensional display device according to claim 5 , wherein the depth suitability determiner adds a correction value, which is larger the closer a distance from the candidate region to the display-forbidden region is, to the difference in depth, and thereupon determines whether or not the difference in depth is within the tolerance range.

7. The three-dimensional display device according to claim 5 , wherein, the shorter a distance between a camera which has imaged the main image and an object displayed in the display-forbidden region, the larger the size of the display-forbidden region.

8. The three-dimensional display device according to claim 5 , further comprising: a possibly-unsuitable region storage, wherein the possibly-unsuitable region decider includes a forbidden region decider that writes the first region and the second region to the possibly-unsuitable region storage as a possibly-unsuitable region.

9. The three-dimensional display device according to claim 1 , wherein the display region candidate decider decides the candidate region giving priority to a candidate at a position closest to the display region of the additional image immediately previously displayed on the screen.

10. The three-dimensional display device according to claim 1 , further comprising: an optimal display plan decider that decides a candidate region at predetermined time intervals, from candidate regions in which the difference in depth is within the tolerance range according to the determination results of the depth suitability determiner regarding whether or not the difference in depth between the depth of the main image and the depth of the additional image is within the tolerance range, for each of the plurality of candidates of the display region of the additional image, at every predetermined time interval, so that from a start of displaying the main image, which is a prerecorded three-dimensional image, to an end of displaying, the distance of movement or number of times of movement of the display region of the additional image is smallest, wherein the image composer composes, as the composite image, an image where the additional image is superimposed on the main image, such that the additional image is displayed at the candidate region for each predetermined time interval decided by the optimal display plan decider, and displays the composite image on the screen.

11. The three-dimensional display device according to claim 10 , wherein the main image is a three-dimensional image imaged by an endoscope camera.

12. The three-dimensional display device according to claim 11 , further comprising: a display-forbidden region storage that stores a display-forbidden region, which is a region on the screen where display of the additional image is forbidden, wherein the display region candidate decider decides one candidate region from the plurality of region candidates of the additional image, which does not overlap the display-forbidden region stored in the display-forbidden region storage, and wherein the display-forbidden region is a region of the main image including an image of an affected area to be treated by surgery.

13. The three-dimensional display device according to claim 1 , wherein the additional image is an image indicating at least one of blood pressure, blood oxygen level distribution, respiration, expiration, body temperature, cardioelectric potential, brainwaves, and pulse waves, of the patient during surgery.

14. The three-dimensional display device according to claim 1 , further comprising: an input that accepts instruction of at least one of a position and a size of the display region of the additional image displayed on the screen, wherein the display region candidate decider decides a candidate region for the display region of the additional image, based on the instruction which the input has accepted.

15. The three-dimensional display device according to claim 14 , wherein the input further accepts instruction to change the size of the display region, and wherein the display region candidate decider changes the size of the candidate region of the display region following the instruction to change the size which the input has accepted.

16. The three-dimensional display device according to claim 14 , wherein the main image is a video of an inside of a body of a patient.

17. The three-dimensional display device according to claim 16 , wherein an image of a surgical instrument is displayed in the main image, and wherein the input accepts input of the position, using information of the position of the surgical instrument in the main image.

18. The three-dimensional display device according to claim 17 , wherein the input includes a passage detector that detects whether or not a tip of the surgical instrument in the main image has passed through the display region of the additional image, and a display control signal generator that, when the passage detector has detected the passage, changes a size of the candidate region of the display region in accordance with a direction of passage of the surgical instrument.

19. The three-dimensional display device according to claim 14 , wherein the input further accepts instruction to change the position of the display region, and wherein the display region candidate decider changes the position of the candidate region of the display region following the instruction to change the position which the input has accepted.

20. The three-dimensional display device according to claim 14 , further comprising: a display-forbidden region storage that stores a display-forbidden region, which is a region on the screen where display of the additional image is forbidden, wherein the display region candidate decider decides the candidate region, which does not overlap the display-forbidden region, based on the instruction which the input has accepted.

21. The three-dimensional display device according to claim 16 , wherein the main image is a video of an inside of a body of a patient, and wherein the additional image is an image of graphs of a plurality of types of biological data of the patient, which changes over time.

22. The three-dimensional display device according to claim 21 , wherein the display region candidate decider decides the candidate region having a shape corresponding to a layout of the graphs of the plurality of types of biological data.

23. The three-dimensional display device according to claim 22 , wherein the layout includes a layout where the graphs of the plurality of types of biological data are arrayed vertically, and a layout where the graphs of the plurality of types of biological data are arrayed horizontally.

24. The three-dimensional display device according to claim 22 , wherein, when the depth suitability determiner determines that the difference in depth of the candidate region is not within the tolerance range even if the position or size is changed, the display region candidate decider changes the layout of the graphs of the plurality of types of biological data.

25. The three-dimensional display device according to claim 14 , wherein the display region candidate decider extracts a portion in the main image where the depth exceeds a predetermined value as being a portion where protrusion from the screen is great, and decides a candidate region of the display region of the additional image to shield the portion where protrusion from the screen is great.

26. A three-dimensional display method for displaying a main image and an additional image on a screen of a three-dimensional display device, the method comprising: deciding, based on a predetermined depth range within the main image, a first region and a second region that are possibly unsuitable for the additional image to be superimposed on the main image, the first region having a depth that protrudes beyond the predetermined depth range toward a near side of the screen, and the second region having a depth that protrudes beyond the predetermined depth range toward a far side of the screen that is recessed relative to the first region; deciding one candidate region from a plurality of region candidates for the additional image to be superimposed on the main image on the screen, wherein the plurality of region candidates includes the first region and the second region decided by the possibly-unsuitable region decider; determining, based on a boundary region that is within a predetermined distance from a boundary line between the candidate region and outside of the candidate region in the main image, whether a difference between a depth of the main image displayed at the boundary region and a depth of the additional image is within a predetermined tolerance range; and superimposing, when it is determined that the difference in depth between the depth of the main image displayed at the boundary region and the depth of the additional image is within the tolerance range, the additional image on the main image, thereby composing, as a composite image, the main image and the additional image, and displaying the composite image on the screen.

27. A non-transitory computer-readable recording medium storing a program causing a computer to execute the three-dimensional display method according to claim 26 .